Technical Field
The present disclosure relates to an asymmetrical cantilever piezoelectric transducer.
Description of the Related Art
The present disclosure is particularly suited for providing piezoelectric microtransducers that may be used in miniaturized energy-harvesting systems suitable for supplying, amongst other things, electronic components and/or devices such as low-consumption sensors and actuators, frequently used in portable electronic devices such as cellphones, tablets, portable computers (laptops), video cameras, photographic cameras, consoles for videogames, and so forth.
As is known, systems for harvesting energy (known as “energy-harvesting systems” or “energy-scavenging systems”) from environmental energy sources have aroused and continue to arouse considerable interest in a wide range of fields of technology. Typically, energy-harvesting systems are designed to harvest and store energy generated by mechanical sources and to transfer it to a generic load of an electrical type. In this way, the electrical load does not require batteries or other power-supply systems that are frequently cumbersome and present a poor resistance to mechanical stresses and entail maintenance costs for interventions of replacement. Further, systems for harvesting environmental energy cover a considerable interest for devices that are in any case provided with battery-supply systems, which, however, present a rather limited autonomy. This is the case, for example, of many portable electronic devices that are becoming of increasingly common use, such as cellphones, tablets, portable computers (laptops), video cameras, photographic cameras, consoles for videogames, etc. Systems for harvesting environmental energy may be used for supplying incorporated components or devices in order to reduce the energy absorbed from the battery and consequently to increase autonomy.
Environmental energy may be harvested from various available sources and converted into electrical energy by purposely provided transducers. For example, available energy sources may be mechanical or acoustic vibrations or, more in general, forces or pressures, chemical energy sources, electromagnetic fields, environmental light, thermal energy sources, etc.
For harvesting and conversion piezoelectric transducers may, amongst other things, be used.
A common type of piezoelectric transducer uses a microstructure comprising a supporting body connected to which are cantilever elements, defined by plane plates constrained to the supporting body at one end and having regions of piezoelectric material at least on a portion of a face. The free ends of the cantilever elements, to which additional masses may be connected, oscillate elastically in response to movements of the supporting body or to vibrations transmitted thereto. As a result of the movements of bending and extension during the oscillations, the piezoelectric material produces a charge that may be harvested and stored in a storage element. Piezoelectric transducers of this kind are suitable for efficiently converting mechanical actions in a direction perpendicular to the faces of the cantilever elements (in the resting condition) in so-called “out of plane” directions. In these directions, in fact, it is possible to obtain maximum bending of the cantilever elements.
However, the response of transducers of this type is practically zero in regard to mechanical actions parallel to the faces of the cantilever elements in so-called “in plane” directions. Disregarding the possibility of using transducers or cantilever elements arranged in different planes (in any case at the expense of a greater occupation of space), the conversion of mechanical energy into electrical energy carried out by the single cantilever element is efficient exclusively in one direction and thus relatively limited.